Low-hanging Fruits And Wedges

April 24, 2008

The other day I promised to bring you part two of Joe Romm's disquisition on the practical feasibility of stabilizing carbon concentrations at 450 ppm. As it happens, his post is live now, and, also as it happens, it's triggered an interesting inter-blog, inter-comment-thread debate between Roger Pielke at the University of Colorado, Boulter, Ted Nordhaus, and Romm himself.

The dispute sounds deceptively simple, but is actually rather complicated: Joe argues that we can wedge down carbon emissions and carbon intensity to sustainable levels with existing and forthcoming technologies if we act quickly. Others think his math is wrong. Well, to my eye, (and this is all a bit above my, ummmm, paygrade) it's not wrong. But also to my eye, all of this math is predicated upon the planet's ability to achieve the following in very short order:

* 1 wedge of vehicle efficiency—all cars 60 mpg, with no increase in miles traveled per vehicle.
* 1 of wind for power—one million large (2 MW peak) wind turbines
* 1 of wind for vehicles—another 2000 GW wind. Most cars must be plug-in hybrids or pure electric vehicles.
* 3 of concentrated solar thermal—~5000 GW peak.
* 3 of efficiency—one each for buildings, industry, and cogeneration/heat-recovery for a total of 15 to 20 million GW-hrs.
* 1 of coal with carbon capture and storage—800 GW of coal with CCS
* 1 of nuclear power—700 GW plus 10 Yucca mountains for storage
* 1 of solar photovoltaics—2000 GW peak [or less PV and some geothermal, tidal, and ocean thermal]
* 1 of cellulosic biofuels—using one-sixth of the world's cropland [or less land if yields significantly increase or algae-to-biofuels proves commercial at large scale].
* 2 of forestry—End all tropical deforestation. Plant new trees over an area the size of the continental U.S.
* 1 of soils—Apply no-till farming to all existing croplands.

Holy massive global undertaking, Batman! Seems to me this will require the sort of co-ordinated and co-operative effort usually reserved for world wars and free-trade agreements and so forth. Moreover, it's hard for me to imagine that by implementing these technologies won't trigger any backward steps--such as, for instance, the all-but-explicit political promise that subsidies for cellulosic ethanol will be paired with subsidies for dirty, dirty corn ethanol. And with backward steps come the need for new wedges and round and round we go. Which is to say that I'm pessimistic--not about the theoretical potential for us to avert this disaster, but for our practical ability to do so.

In the end, though, I think everyone's in basic agreement: We should pick the low hanging fruit now and we should invest a ton of money, intelligently, in underdeveloped clean technologies. And waiting any longer is a terrible, terrible idea.